1. Field of the Invention
The present invention relates to a printing apparatus. Particularly, the present invention relates to a printing apparatus which prints by converting input print data.
2. Description of the Related Art
Recent printing apparatuses using printheads are available not only as a single-function printer which prints based on print data transferred from a host apparatus, but also as a multi-function printer (MFP) having scanner and copy functions.
In order to provide many functions, a multi-function printer includes a larger number of components and has a more complicated structure, compared to a single-function printer. Such multi-function printers particularly require various kinds of interfaces because their print data supply source ranges from a host apparatus to a scanner unit and memory card. However, a single printing unit prints using print data from a variety of supply sources. The multi-function printer needs to appropriately perform image processing for print data from a plurality of print data supply sources to supply print data to a printhead serving as a final printing means.
For example, when performing trial print of an image document read by the scanner unit of a multi-function printer, the multi-function printer thins image data from the scanner unit to generate print data. This thinning processing uses mask data (mask pattern). The thinning processing generally adopts a simple mask pattern, like zigzag thinning (see, e.g., Japanese Patent Laid-Open No. 8-20125). The thinning processing uses a plurality of mask patterns in accordance with the thinning rate.
Thinning processing using mask data (mask pattern) is also applied to so-called multi-pass printing to print a high-quality image. In this case, every time the printhead is scanned, the mask pattern is changed to use a different one.
Many different mask patterns are necessary to implement various functions of multi-function printers, and require a storage area for holding mask pattern data in the printer. Mask processing needs a large buffer area for bitmapping a mask pattern.
For this reason, multi-function printers suffer a large memory capacity to store a mask pattern. In addition, separate image processes each using a mask pattern increase the size of a data processing circuit such as an ASIC.